By my own admission, I am pretty slapdash in many areas of my life, but international travel is the one area in which I am really meticulous.
I have never forgotten anything at check in, but I did once, and once only forget something at security checkout!
If you have you have ever been to HCMC (Saigon), it's not uncommon to have to go through a security scan upon arrival,
I never let vital stuff leave my person when travelling, so passport, cards, travel docs and keys live in a body belt. This also has to be removed and put through the scanner, as well as your bags.
Through I went, collected my bags, and went to the arrivals area to organise myself. I intended to take a taxi to the hotel, so went to pull out my booking form to show the driver the address - no body belt. Talk about blood running cold!
Ran back to security, and there it was lying on a table at the end of the scanner. Never again.